The authors have no conflict of interest
Dietary Calcium and Phosphorus Ratio Regulates Bone Mineralization and Turnover in Vitamin D Receptor Knockout Mice by Affecting Intestinal Calcium and Phosphorus Absorption†
Article first published online: 1 JUL 2003
Copyright © 2003 ASBMR
Journal of Bone and Mineral Research
Volume 18, Issue 7, pages 1217–1226, July 2003
How to Cite
Masuyama, R., Nakaya, Y., Katsumata, S., Kajita, Y., Uehara, M., Tanaka, S., Sakai, A., Kato, S., Nakamura, T. and Suzuki, K. (2003), Dietary Calcium and Phosphorus Ratio Regulates Bone Mineralization and Turnover in Vitamin D Receptor Knockout Mice by Affecting Intestinal Calcium and Phosphorus Absorption. J Bone Miner Res, 18: 1217–1226. doi: 10.1359/jbmr.2003.18.7.1217
- Issue published online: 2 DEC 2009
- Article first published online: 1 JUL 2003
- Manuscript Accepted: 2 DEC 2002
- Manuscript Revised: 15 OCT 2002
- Manuscript Received: 13 MAR 2002
- bone mineral density;
- bone mineral content;
- calcium absorption;
- bone formation;
The effects of the dietary Ca and P ratio, independent of any vitamin D effects, on bone mineralization and turnover was examined in 60 VDRKO mice fed different Ca/P ratio diets. High dietary Ca/P ratio promoted bone mineralization and turnover with adequate intestinal Ca and P transports in VDRKO mice.
Introduction: To clarify the effects of the dietary calcium (Ca) and phosphorus (P) ratio (Ca/P ratio) on bone mineralization and turnover in null-vitamin D signal condition, vitamin D receptor knockout (VDRKO) mice were given diets containing different Ca/P ratios.
Materials and Methods: Five groups of 4-week-old VDRKO mice, 10 animals each, were fed diets for 4 weeks. Group 1 was wild-type littermate mice, fed the diet containing 0.5% Ca and P (Ca/P = 1). Group 2 was the control and was fed a similar diet (Ca/P = 1). Groups 3, 4, 5, and 6 were fed the following diets:0.5% Ca and 1.0% P (Ca/P = 0.5), 1.0% Ca and 1.0% P (Ca/P = 1), 1.0% Ca and 0.5% P (Ca/P = 2), and 0.5% Ca and 0.25% P (Ca/P = 2).
Results and Conclusions: Compared with group 2, serum calcium and phosphorus levels in groups 4–6 significantly increased. Serum parathyroid hormone levels increased in group 3 and decreased in group 5. The amounts of intestinal calcium absorption decreased in groups 3 and 4. Phosphorus absorption increased in group 3 and decreased in groups 4–6. Bone mineral content (BMC) and bone mineral density (BMD) of the femur in group 3 significantly decreased and increased in group 5. In the primary spongiosa of the proximal tibia, the trabecular bone volume (BV/TV) and osteoid thickness (O.Th) in group 3 significantly increased, and decreased in group 6. In groups 5 and 6, the numbers of the trabecular osteoclasts increased. In groups 2 and 4, and the secondary spongiosa was identified in 5 of 10 mice. In group 3, there was no secondary spongiosa in either mouse. Osteoid maturation time (OMT) significantly decreased, and bone formation rate (BFR/BS) increased in groups 4–6. These data indicate that the dietary Ca/P ratio regulates bone mineralization and turnover by affecting the intestinal calcium and phosphorus transports in VDRKO mice. They may suggest the existence of Ca/P ratio-dependent, vitamin D-independent calcium and phosphorus transport system in the intestine.